Rotatable cable guide with cable switching feature

Abstract

A cage in which two pulley wheels are mounted with tangent circumferences so that their circumferential cable grooves surround a cable passing between the wheels. The cage freely rotates about an axis that passes between the wheels. The cage axis is normal to the plane of the parallel wheel axes. The cage extends forward of the wheels and forms two curved edges on opposed sides of the cage axis. Each curve has an apex at its forward-most point. A flexible cable passes through the cage, between the wheels, and forward between the curves. Extending the cable substantially away from the plane of the wheels causes it to contact one of the curves. This rotates the cage so that the wheels are aligned with the cable deflection. This switches the cable to one or the other of the wheels, and provides low friction cable operation for any cable direction.

1. A cable guide, comprising:
 a rotatable cage having front and back ends, a rotation axis passing through the front and back ends of the cage, and a cable channel along the cage rotation axis; 
 a slot dividing the front of the cage, the slot having first and second opposed side surfaces; 
 two pulley wheels rotatably mounted in the slot on opposite sides of the cage axis, each wheel having a rotation axis, the wheel axes substantially parallel to each other defining a plane normal to the cage axis, each wheel having a circumference and a continuous circumferential groove, the wheels being mounted adjacent to each other with approximately mutually tangent circumferences; and 
 the front end of the cage extending forward of the wheels, and forming a respective first and second curved edge with each respective side surface of the slot, each curved edge having an apex that is the forward-most point on the edge and also the point on the edge that is nearest the cage axis; 
 
     whereby a cable can pass through the cage, between the two wheels, and a deviation of the cable forward of the wheels that is sufficient to contact either of the curved edges tends to rotate the cage, causing the wheels to align with the plane of the deviation, and causing the cable to fall into the respective groove in one or the other of the wheels. 
   
   
     2. The cable guide of  claim 1 , wherein each pulley wheel extends laterally outside the cage sufficiently that a flexible cable passing forward through the cable passage can be redirected up to at least 170 degrees around either of the pulley wheels without interference from the case. 
   
   
     3. The cable guide of  claim 1 , wherein both pulley wheels have approximately the same diameter, and the apexes of the curved edges are within a range of distances of 0.7 to 1.4 wheel diameters forward of the pulley wheel axes. 
   
   
     4. The cable guide of  claim 3 , wherein each of the curved edges follows a conic section curve of a type having a vertex, the vertex of the conic section curve forming the apex of the curved edge. 
   
   
     5. The cable guide of  claim 3 , wherein each of the curved edges follows part of a plane curve selected from the set consisting of: a circle, a parabola, a hyperbola, an ellipse, and two generally straight lines meeting and rounded at the apex. 
   
   
     6. A cable guide comprising:
 a rotatable cage having a front end, a back end, a rotation axis passing through the front and back ends of the cage, a cable passage along the cage rotation axis that is open to the front and back ends of the cage; 
 a slot in the cage passing transversely across the cage axis, open on the front of the cage, open on opposite sides of the cage, and having first and second opposed side surfaces; 
 first and second pulley wheels, each wheel having an axis and a continuous circumferential groove for a cable, the two wheels rotatably mounted in the slot on opposite sides of the cage axis with approximately tangent circumferences, aligned grooves, and substantially parallel axes; 
 the cage front extending forward of the pulley wheels; and 
 the cage front intersecting the first and second side surfaces of the slot to form respective first and second cable switching curves; 
 each of the cable switching curves having an apex at the forward-most point on the curve; 
 
     whereby a cable can pass axially through the cage between the two wheels, and a deviation of the cable forward of the wheels that is sufficient to contact either of the switching curves tends to rotate the cage, causing the slot to align with the plane of the deviation, and causing the cable to ride in the groove in one or the other of the wheels. 
   
   
     7. The cable guide of  claim 6 , wherein each pulley wheel extends laterally outside the cage sufficiently that a flexible cable passing forward through the cable passage can be redirected up to at least 170 degrees around either of the pulley wheels without interference from the case. 
   
   
     8. The cable guide of  claim 6 , wherein both pulley wheels have approximately the same diameter, and the apexes of the cable switching curves are within a range of distances of 0.7 to 1.4 wheel diameters forward of the wheel axes. 
   
   
     9. The cable guide of  claim 8 , wherein each of the cable switching curves follows a conic section curve of a type having a vertex, the vertex of the conic section curve forming the apex of the curved edge. 
   
   
     10. The cable guide of  claim 8 , wherein each of the cable switching curves is part of a plane curve selected from the set consisting of: a circle, a parabola, a hyperbola, an ellipse, and two generally straight lines meeting and rounded at the apex. 
   
   
     11. A cable guide comprising:
 a rotatable cage with generally cylindrical sides, a front surface, a back surface, a rotation axis substantially coincident with the geometric axis of the cylindrical sides, and a cable passage through the case around the cage rotation axis; 
 a slot crossing and dividing the front surface of the cage, open on opposite sides of the cage, the slot having first and second opposed side surfaces; 
 first and second pulley wheels rotatably mounted in the slot on opposite sides of the cage rotation axis, each wheel having a rotation axis and a circumferential groove, the two wheel axes substantially parallel to each other in a plane substantially normal to the cage rotation axis, both wheels having substantially the same diameter; 
 the front surface of the cage intersecting the side surfaces of the slot along respective first and second curved edges; 
 each curved edge having an apex at the forwardmost point on the edge, the apex being within a range of 0.7 to 1.4 wheel diameters forward of the plane of the wheel axes, each curved edge sloping backward and outward in two directions from the apex, and 
 each pulley wheel extending laterally outside the cage sufficiently that a flexible cable passing forward through the cable passage can be redirected up to at least 170 degrees around either of the pulley wheels without interference from the case; 
 
     whereby a cable can pass axially through the cage between the two wheels, and a deviation of the cable forward of the wheels that is sufficient to contact either of the curved edges tends to rotate the cage, causing the slot to align with the plane of the deviation, and causing the cable to fall into the groove in one or the other of the wheels. 
   
   
     12. The cable guide of  claim 11 , wherein each of the curved edges follows a conic section curve of a type having a vertex, the vertex of the conic section curve forming the apex of the curved edge. 
   
   
     13. The cable guide of  claim 11 , wherein each of the curved edges follows part of a plane curve selected from the set consisting of: a circle, a parabola, a hyperbola, an ellipse, and two generally straight lines meeting and rounded at the apex. 
   
   
     14. The cable guide of  claim 11 , wherein each of the curved edges follows a part of an ellipse with the major axis of the ellipse parallel to the rotation axis of the cage and a vertex of the ellipse being the apex of the curved edge.